Thermal atomic layer etching processes

ABSTRACT

Thermal atomic layer etching processes are disclosed. In some embodiments, the methods comprise at least one etch cycle in which the substrate is alternately and sequentially exposed to a first vapor phase halide reactant and a second vapor halide reactant. In some embodiments, the first reactant may comprise an organic halide compound. During the thermal ALE cycle, the substrate is not contacted with a plasma reactant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional application No.62/432,318, filed Dec. 9, 2016, U.S. Provisional application No.62/449,945, filed Jan. 24, 2017, U.S. Provisional application No.62/455,989, filed Feb. 7, 2017, and U.S. Provisional application No.62/485,330, filed Apr. 13, 2017.

BACKGROUND OF THE INVENTION

Field of the Invention

The present application relates to etching processes, more particularlyto thermal atomic layer etching processes using sequential reactions.

Description

Vapor deposition processes such as atomic layer deposition (ALD) arewell-known. ALD processes typically utilize alternating and sequentialpulses of vapor-phase reactants to deposit up to a monolayer of materialin a controlled and highly-conformal manner. Thin films deposited by ALDare used in a wide variety of applications, such as in the formation ofintegrated circuits. Controlled removal of materials is also highlydesirable. In contrast to ALD, atomic layer etching (ALE) utilizessequential pulses of vapor phase reactants to remove material from asubstrate in each reaction cycle. Typical ALE processes utilize a firstreactant to form a first species on the substrate surface that is thenremoved by a second, excited species generated from a plasma.

SUMMARY OF THE INVENTION

In some embodiments, a film on a substrate is etched in a reactionchamber by a chemical atomic layer etching process comprising one ormore etch cycles. Each etch cycle comprises exposing the substrate to afirst vapor-phase halide reactant, such as a non-metal halide reactant,to form adsorbed species on the substrate surface and subsequentlyexposing the substrate to a second vapor-phase reactant, wherein thesecond vapor-phase reactant converts the adsorbed species into volatilespecies that comprise one or more atoms from the surface to be etched.In this way at least some material is removed from the film in each etchcycle.

In some embodiments, the first vapor-phase halide reactant, such asnon-metal halide reactant comprises a first halide ligand and the secondvapor-phase reactant comprises a second halide ligand. In someembodiments, the substrate is not contacted with a plasma reactantduring the etching cycle. In some embodiments, the etching cycle isrepeated two or more times. In some embodiments the first vapor-phasehalide reactant may comprise metal.

In some embodiments, the volatile adduct comprises an atrane compound.In some embodiments, the atrane compound is formed fromtris(2-aminoethyl)amine or triethanolamine.

In some embodiments, the film comprises at least one of W, TiN, TiO₂,TaN, SiN, SiO_(X), AlO_(x), AlO₂, Al₂O₃, ZrO_(x), ZrO₂, WO₃, SiOCN,SiOC, SiCN, AlN and HfO₂.

In some embodiments, the surface to be etched comprises a metal nitridesuch as TiN or TaN and the second vapor-phase reactant comprises a Lewisacid.

In some embodiments, the first vapor-phase halide reactant comprises ametal halide. In some embodiments, the metal comprises Nb, Ta, Mo, Sn,V, Re, W, or group 5 or 6transition metal. In some embodiments, thefirst vapor-phase halide reactant comprises Sb or Te. In someembodiments, the halide comprises chlorides, fluorides, bromides, oriodides. In some embodiments, the first vapor-phase halide reactantcomprises NbF₅.

In some embodiments, the first vapor-phase halide reactant does notcomprise a metal. In some embodiments, the first vapor-phase halidereactant comprises an organic halide compound. In some embodiments, thefirst vapor-phase halide reactant comprises an alkyl halide, an acylhalide, a sulfonyl halide, a sulfenyl halide, a selenyl halide, or aboron halide comprising an organic ligand.

In some embodiments, the first vapor-phase halide reactant comprisesfluorosulfonic acid, trifluoromethanesulfonic acid, trifluoromethyltrifluoromethanesulfonate, or 1-chloro2-(pentafluorosulfuranyloxy)ethane.

In some embodiments, the first vapor-phase reactant compriseschlorosulfonyl isocyanate or N,N-dimethylsulfamoyl chloride.

In some embodiments the first vapor-phase reactant comprises boron,hydrogen and a halide. In some embodiments, the second vapor-phasehalide reactant comprises phosphorous, oxygen, and a halide. In someembodiments, the first vapor-phase halide reactant comprises antimonyand a halide.

In some embodiments, the first vapor-phase halide reactant comprises oneor more CF₃ groups.

In some embodiments a first vapor-phase halide reactant may comprise acyclic compound like cyclohexanedienes (chd), cyclopentadiene etc. Insome embodiments first reactant may comprise of α,β-unsaturated carbonylcompounds, for example enones like methyl vinyl ketone etc.

In some embodiments, the second vapor-phase reactant comprises a Lewisbase. In some embodiments, the Lewis base comprises a pyridine,tetra-hydro furan (thf), DMSO, tetra-hydro-thiophene, a pyrrole, animidazole, a thiazine, or an azines such as pyrazine. In someembodiments, the second vapor-phase reactant comprises a diamine ordithione. In some embodiments, the second vapor-phase reactant comprisesa heterocyclic reactive compound. In some embodiments, the heterocycliccompound comprises a thiocarbonate, thiadiazole, or dioxane.

In some embodiments, the second vapor-phase reactant comprises a planarcompound such as BCl₃, BF₃, or AlCl₃. In some embodiments the secondvapor-phase reactant comprises a halide. In some embodiments, the secondvapor-phase reactant comprises more than two halides.

In some embodiments, the second vapor-phase reactant comprises SO₃, analkyl isothiocyanate such as CH₃NCS, chloronitrile, COS, or CS₂.

In some embodiments, second vapor-phase reactant is capable of formingcoordinated bonds to a metal atom that has adsorbed to the substratesurface.

In some embodiments, the second vapor-phase reactant does not comprisemetal. In some embodiments the second vapor-phase halide reactant is acarbon based halide. In some embodiments the carbon based halidecomprises CCl₄ or CBr₄.

In some embodiments, the etching cycle comprises exposing the substrateto a first vapor-phase reactant and subsequently exposing the substrateto a second vapor-phase reactant, wherein the substrate is not contactedwith a plasma reactant during the etching cycle. In some embodiments,the first vapor-phase reactant comprises CSe₂. In some embodiments, thefirst vapor-phase reactant comprises compounds with S═R═S structure inwhich R can be carbon or any hydrocarbon, such as C2-C8. In someembodiments, the first vapor-phase reactant comprises CS₂. In someembodiments, CS₂ takes part in in-situ formation of etchants. In someembodiments the second vapor-phase reactant comprises TEA or TMA.

In some embodiments a process for etching a thin film on a substrate ina reaction chamber comprises sequentially exposing the substrate to avapor-phase halide reactant, wherein the vapor-phase halide reactant isnot an alkylhalide comprising hydrogen, and wherein the process is notself-limiting.

In some embodiments the temperature of the substrate during the etchingcycle is 300 to 500° C.

In some embodiments a method for etching a film on a substrate surfacecomprises exposing the substrate surface to a first vapor-phase halidereactant comprising a first halide ligand to form first reactant specieson the substrate surface, wherein the first vapor-phase halide reactantdoes not comprise hydrogen. The substrate may be subsequently exposed toa second vapor-phase halide reactant comprising a second halide ligandsuch that the second vapor-phase halide reactant converts the firstreactant species to vapor phase reaction products, wherein the secondvapor-phase halide reactant does not comprise hydrogen. In someembodiments the formation of the first reactant species and/or theconversion of the second vapor-phase halide reactant to vapor phasereaction products are not self-limiting. In some embodiments thesubstrate is not exposed to a plasma reactant during the etching cycle.In some embodiments the substrate is exposed to a third vapor phasereactant that is different from the first and second vapor-phasereactants in one or more etch cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart generally illustrating a method for thermalatomic layer etching in accordance with some embodiments.

FIG. 2 is a flow chart generally illustrating a method for thermalatomic layer etching using chloride reactants in accordance with someembodiments.

FIG. 3 is a flow chart generally illustrating a method for thermalatomic layer etching using NbF₅ and CCl₄ as reactants in accordance withsome embodiments.

FIG. 4 is a flow chart generally illustrating a method for thermalatomic layer etching using a first halide reactant and a second organicreactant in accordance with some embodiments.

FIG. 5 is a flow chart generally illustrating a method for thermalatomic layer etching using a first halide reactant and a second adductforming reactant in accordance with some embodiments.

FIG. 6 is a graph showing the differences in mass, thickness, and sheetresistance of SiO₂, TiN, AlN, TiO₂, SiN, TaN, ZrO₂, and Al₂O₃ filmsafter ALE processing using NbF₅ and CCl₄ as reactants.

FIG. 7 is a graph showing the weight and sheet resistance of substratescomprising TiN and TaN films after varying numbers of ALE cycles usingNbF₅ and CCl₄ as reactants.

FIG. 8 is a graph showing the removed mass for AlN, TiN, HFO₂, and TaNfilms after ALE processing using a variety of reactants and etchingtemperatures in accordance with some embodiments.

FIG. 9 is a graph showing the removed mass for TiN, AlN, AlOx, HfOx,TaN, SiN, and thermal oxide films after ALE processing using a varietyof etch reactants and etching temperatures in accordance with someembodiments.

DETAILED DESCRIPTION

A sub-monolayer or more of material can be removed from a substrate byatomic layer etching (ALE) processes comprising alternately contactingthe substrate surface in a reaction space with first and secondvapor-phase reactants. In some embodiments of ALE-type processes, one ormore etch cycles are provided comprising a saturative, self-limitingadsorption step in which the substrate is contacted with a firstvapor-phase reactant followed by a second exposure step in which thesubstrate is contacted with a second vapor-phase reactant. In the firstadsorption step the first reactant adsorbs, typically in a self-limitingmanner, to the material to be etched on the substrate surface. Thesecond exposure step then leads to the formation of volatile by-productsthat contain the adsorbate atoms, atoms of the second reactant and someatoms from the surface being etched. In this way the etching of thedesired material on the substrate surface can be carefully controlled.In some embodiments the second reactant forms volatile adducts thatinclude atoms from the surface being etched.

An adduct can be considered, for example, as a chemical species AB, eachchemical or molecular entity of which is formed by direct combination oftwo separate chemical or molecular entities A and B in a way that thereis change in the way the chemical or molecular entities connect, but noloss of atoms within the chemical entities A and B.

In some embodiments surface contaminations may be removed from asubstrate surface, such as B or C contamination. In this contextcontaminations can be any unwanted atoms on the surface or film, forexample metal contaminants, S, O etc. In some embodiments contaminationsmay be removed from a substrate surface or from the film itself duringdeposition step by additional selective etching step added every nthcycle of deposition cycles.

In some embodiments, the target material to be etched comprises a metal,such as Ti, Ta, Al, Zr or Hf, W. In some embodiments, the material to beetched comprises one or more of W, TiN, TiO₂, TaN, SiN, SiO_(X),AlO_(x), AlO₂, Al₂O₃, ZrO_(x), ZrO₂, WO₃, AlN, HfO_(x) and HfO₂. In someembodiments, the material to be etched comprises metal nitride or metaloxide or mixtures thereof. In some embodiments the material to be etchedmay comprise Si, Ge, a-C, graphene, polymers, SiO_(x), metals, includingPt, Fe, Cu, Au, and Zn in addition to the metals provided above.

In some embodiments, gas phase reactions are avoided by feeding thereactants alternately and sequentially into the reaction chamber. Vaporphase reactants are separated from each other in the reaction chamber.In some embodiments this may be accomplished, for example by removingexcess reactants and/or reaction by-products from the reaction chamberbetween reactant pulses. In some embodiments the reactants may beremoved from proximity with the substrate surface with the aid of apurge gas and/or vacuum. In some embodiments excess reactants and/orreactant byproducts are removed from the reaction space by purging, forexample with an inert gas. In some embodiments purging comprisesexposing the substrate surface to a purge gas, such as an inert gas.Because of the separation of reactants and the self-limiting nature ofthe reactions, less than a monolayer of material is typically removed ineach ALE etch cycle. However, in some embodiments more than onemonolayer may be removed in each cycle. In some embodiments thereactions may not be self-limiting or saturating. In some embodiments,at least one of the phases, such as in exposure to a first vapor phasereactant, second vapor phase reactant or the reactants in the additionalphases, the reaction, such as etching reactions, are not self-limitingor saturating. In some embodiments pulses of reactants may partially orcompletely overlap. For example, in some embodiments one reactant mayflow continuously into the reaction space while one or more additionalreactants are provided intermittently, at desired intervals.

The ALE methods disclosed herein are thermal etching processes, asopposed to plasma etching processes. Thus, plasma reactants are not usedin the ALE etch cycles. While referred to as thermal ALE processes todifferentiate processes that use plasma reactants, in some embodiments,the ALE reactions may have zero activation energy and therefore may notrequire any additional thermal energy. Thus the reactions may also bereferred to as chemical etching processes herein. Thermal ALE methodscan be more desirable in some situations than plasma ALE methods becausethermal ALE methods can be less damaging to the underlying substrate.Also, thermal ALE methods allows for isotropic etching of non-line ofsight (NLOS) features.

The ALE processes disclosed herein utilize particular reactants orcombinations of reactants that have been found to allow for controlledetching in the absence of the use of plasma. In some embodiments, metalhalides, such as transition metal halides, for example halides such aschlorides, fluorides, bromides or iodides of group 5 or 6 transitionmetal halides, are used as a first reactant and are contacted to thesubstrate in a first self-limiting adsorption step. The metal in thefirst reactant may be, for example, Nb, Ta, Mo, Sn, V, Re, Te, or W. Insome embodiments, the metal halide first reactant is a metal chloride,such as NbCl₅, SnCl₄, TaCl₅, MoCl_(x) where x is from about 3 to 5, orWCl_(x) where x is from about 4 to 6. In some embodiments, the metalhalide first reactant is a metal fluoride, such as NbF₅, TaF₅, WF₆, VF₅,ReF₆, ReF₇, or MoF₆. In some embodiments, a non-metal or semi-metalfluoride like TeF₆, SbF₅ or AsF₅ can be used as first reactant. In someembodiments, the metal halide may be a metal bromide or metal iodide,such as SnBr₄, SnI₄.

In some embodiments, the first reactant may comprise a halide that isnot a metal halide.

In some embodiments, the first reactant may comprise an organic halidecompound. For example, in some embodiments, the first reactant maycomprise an alkyl halide compound. In some embodiments, the firstreactant may comprise an aromatic, saturated, or unsaturated aliphaticalkyl halide compound comprising two or more carbon atoms. In someembodiments, the first reactant may comprise a substituted alkyl halide,for example in some embodiments, the first reactant may comprisetert-butyl chloride, 1,1-dichloroethane, 1,2-dichloroethane, ortrichloroethane, trifluoroethanol, trifluoroisopropanol. In someembodiments, the first reactant may comprise an aromatic, saturated, orunsaturated aliphatic alkene halide compound. For example, in someembodiments, the first reactant may comprise a substituted vinyl halide,or an allyl halide.

In some embodiments, the first reactant may comprise organic oxyhalide.In some embodiments, the first reactant may comprise an acyl halidecompound, such as an aromatic, saturated, or unsaturated aliphatic acylhalide compound, including di, and tri acyl halides. For example, insome embodiments, the first reactant may comprise fumaryl chloride,malonyl chloride, succinyl, or oxalyl halide. In some embodiments, thefirst reactant may comprise terephthaloyl chloride. In some embodiments,the first reactant may comprise 1,3,5-Benzenetricarbonyl trichloride.

In some embodiments, the first reactant may comprise a sulfonyl halide,such as an aromatic, saturated, or unsaturated aliphatic sulfonylhalide. In some embodiments, the first reactant may comprise, forexample, ethanesulfonyl fluoride (C₂H₅FO₂S), methanesulfonyl chloride(CH₃ClO₂S), methanesulfonyl fluoride (CH₃FO₂S), phenylsulfonyl fluoride(PhFO₂S), pyridinesulfonyl fluoride (C₅H₄FNO₂S), thiophenesulfonylfluoride (C₄H₃FO₂S₂), cyanomethanesulfonyl chloride (C₂H₂ClNO₂S),chloromethanesulfonyl chloride (ClCH₂SO₂Cl), or trifluoromethanesulfonylchloride (CF₃SO₂Cl) etc. In some embodiments, the first reactant maycomprise a sulfenyl halide compound or selenenyl halide compound. Forexample, in some embodiments, the first reactant may comprisetrichloromethanesulfenyl chloride (CCl₃SCl), or chlorocarbonylsulfenylchloride (ClCOSCl). In some embodiments, the first reactant may comprisea compound having the formula PhSeCl, wherein Ph is a phenyl group. Insome embodiments, the first reactant may comprise a compound having theformula RSeX, wherein R is an alkyl ligand and X is a halide.

In some embodiments, the first reactant may comprise sulfur, carbon, andone or more halide atoms, such as thiophosgene (CSCl₂).

In some embodiments, the first reactant may comprise sulfur,phosphorous, and one or more halide atoms, such as thiophosphorylchloride (PSCl₃) and thiophosphoryl fluoride (PSF₃).

In some embodiments, the first reactant may comprise phosphorous and oneor more halide atoms.

In some embodiments, the first reactant may comprise sulfur, nitrogenand one or more halide atoms, such as thiazyl chloride, thiazylfluoride, thiazyl trifluoride (NSF₃).

In some embodiments, the first reactant may comprise phosphorous, oxygenand one or more halide atoms, such as phosphoryl chloride (POCl₃).

In some embodiments, the first reactant may comprise a ligand,phosphorous, oxygen and one or more halides. In some embodiments thefirst reactant may have the general formula ligand-POX₂. Exemplaryligands include dialkyl amido (e.g. N,N-dimethylphosphoramicdichloride), phenyl (e.g. phenylphosphoryl dichloride) and alkyl (e.g.tert-butylphosphonyl dichloride and methylphosphonyl dichloride).

In some embodiments, the first reactant may comprise a ligand,phosphorus and one or more halides. In some embodiments the firstreactant may have the general formula ligand-PX₂, wherein X is halideincluding not just chlorine and fluorine. For example, the firstreactant may comprise dimethylphosphoramidous dichloride.

In some embodiments, the first reactant may comprise sulfur and carbon.In some embodiments, the first reactant may comprise an S═R═S structurein which R can be carbon or any hydrocarbon, such as C2-C8 hydrocarbon.For example, in some embodiments the first reactant may comprise carbondisulfide (CS₂) or carbon diselenide (CSe₂). In some embodiments thefirst reactant may form adducts with transition metals incorporated inthe substrates.

In some embodiments, the first reactant may comprise a compoundcomprising oxygen and sulfur and a halide and hydrogen or a hydrocarbongroup, such as alkyl group.

In some embodiments, the first reactant may comprise a sulfinyl halide,such as an aromatic or aliphatic or substituted aromatic or substitutedaliphatic, saturated, or unsaturated sulfinyl halide. In someembodiments, the first reactant may comprise, for example,trichloromethanesulfinyl chloride, trifluoromethanesulfinyl fluoride,trifluoromethanesulfinyl chloride, tert-butylsulfinyl chloride.

In some embodiments, the first reactant may comprise a sulfonic acidhalide compound such as an aromatic or aliphatic or substituted aromaticor substituted aliphatic, saturated, or unsaturated sulfonic acidhalide. For example, in some embodiments, the first reactant maycomprise fluorosulfonic acid (FSO₃H) and/or trifluoromethanesulfonicacid (CF₃SO₃H).

In some embodiments, the first reactant may comprise a sulfonatecompound, such as an aromatic or aliphatic or substituted aromatic orsubstituted aliphatic, saturated, or unsaturated sulfonate halide. Forexample, in some embodiments, the first reactant may comprisetrimethylsilyl trifluoromethanesulfonate (C₄H₉F₃O₃SSi) andtrifluoromethyl trifluoromethanesulfonate (CF₃SO₃CF₃).

In some embodiments, the first reactant may comprise a substitutedsulfur triflouride having the formula A-SF₃, wherein A can bedimethylsulfide, diethylsulfide, benzene, alkyl group, pyridine,thiophene, cyclopropane, or aminato groups including methylmethanaminatoin trifluoro(N-methylmethanaminato)sulfur.

In some embodiments, the first reactant may comprise a sulfuranecompound having the formula X—O—SF_(y), wherein X is an alkyl ligand, anaromatic ligand or a halide and y is from 1 to 5. For example, in someembodiments, the reactant may comprise 1-chloro2-(pentafluorosulfuranyloxy)ethane (SF₅OC₂H₂Cl).

In some embodiments, the first reactant may comprise sulfur, oxygen anda halide, such as chlorine or fluorine, and a hydrocarbon and mayinclude cyclic alkyl group, for example a cyclopropyl group e.g.cyclopropylthionylchloride.

In some embodiments, the first reactant may comprise a reactant withgeneral formula Ligand-CCl₃. In some embodiments, the first reactant maycomprise nitrogen, a halide, carbon and oxygen. For example, thereactant may comprise trichloronitromethane (CCl₃NO₂) or trichloroacetylisocyanate (Cl₃CCONCO).

In some embodiments, the first reactant may comprise hydrogen, halide,carbon and oxygen. In some embodiments, the first reactant may comprise,for example, an alkyl chloroformate such as ethyl chloroformate, methylchloroformate, propyl chloroformate, chloromethyl chloroformate, or2,2,2-trichloroethoxycarbonyl chloride.

In some embodiments, the first reactant may comprise nitrogen, hydrogen,halide, carbon and oxygen. In some embodiments, the first reactant maycomprise, for example, trichloroacetamide or substitutedtrichloroacetamide (O-Allyl 2,2,2-trichloroacetimidate).

In some embodiments, the first reactant may comprise nitrogen, halide,and carbon. In some embodiments, the first reactant may comprise, forexample, trichloroacetonitrile.

In some embodiments, the first reactant may comprise nitrogen, carbon,sulfur, a halide and oxygen.

In some embodiments, the first reactant may comprise carbon, sulfur, ahalide, hydrogen and oxygen.

In some embodiments, the first reactant may comprise nitrogen, carbon,sulfur, a halide, hydrogen and oxygen. In some embodiments, the firstreactant may comprise chlorosulfonyl isocyanate, chloromethylchlorosulfate, or N,N-dimethylsulfamoyl chloride.

In some embodiments, the first reactant may comprise a halogen andsuccinimide group. In some embodiments, for example, the first reactantmay comprise N-Chlorosuccinimide, N-Bromosuccinimide.

In some embodiments, the first reactant may comprise boron, a halide andhydrogen. In some embodiments, the first reactant may comprise boron,fluorine and hydrogen. In some embodiments, the first reactant maycomprise HBF₄, for example. In some embodiments HBF₄ is used as acomplex compound, when the first reactant is not in vaporized form inthe reactant source vessel.

In some embodiments, the first reactant may comprise a boron trihalidein a stabilizer, wherein the stabilizer may be, for example and withoutlimitation, alkylamine, alkylnitrile, water, or dimethylsulfide, orother compound that may form either volatile complexes or adducts withboron trihalides. In some embodiments, the first reactant may comprise,for example, a boron trifluoride ethylamine complex.

In some embodiments, the first reactant may comprise a boron halide ofgeneral formulae BX_(a)Y_(b), wherein ‘a’ and ‘b’ can be greater than orequal to zero, or greater than or equal to one, and wherein X and Y canbe halide, including fluorine, chlorine and bromine and iodine. Thefirst reactant may be stabilized in an organic stabilizer containing atleast one carbon, oxygen or hydrogen, including, for example, ethanol,diethyl ether, dimethyl ether, dimethylsulfide.

In some embodiments, the first reactant may comprise a tetrafluoroboricacid diethyl ether complex. In some embodiments, the first reactant maycomprise, for example, trifluoride dihydrate. In some embodiments, thefirst reactant may comprise, for example, Boron trifluoridetetrahydrofuran complex.

In some embodiments, the first reactant flows continuously during theetch cycles or in a cyclic fashion into the reactor.

In some embodiments, the first reactant may comprise antimony and ahalide, such as fluorine. In some embodiments, the first reactant maycomprise antimony, fluorine and hydrogen. In some embodiments, the firstreactant may comprise antimony, fluorine, oxygen and nitrogen. In someembodiments, the first reactant may comprise antimony, fluorine andoxygen. In some embodiments, the first reactant may comprise antimony,fluorine and at least one ligand other than antimony or fluorine. Insome embodiments, the first reactant may comprise a fluoroantimonic saltcompound. For example, in some embodiments, the first reactant maycomprise hexafluoro antimonic acid (HSbF₆), nitroniumhexafluoroantimonate NO₂SbF₆, nitrosonium hexafluoroantimonate (NOSbF₆),or hexafluoroantimonic acid hydrate (HSbF₆.6H₂O).

In some embodiments, the first reactant may comprise phosphorus andoxygen. In some embodiments, the first reactant may comprise phosphorus,oxygen and hydrogen. In some embodiments, the first reactant maycomprise phosphorus, oxygen and a halide such as fluorine. In someembodiments, the first reactant may comprise phosphorus, oxygen and ahydrocarbon group, such as an alkyl group. In some embodiments, thefirst reactant may comprise a phosphate compound. For example, in someembodiments, the first reactant may comprise ammoniumhexafluorophosphate.

In some embodiments, the first reactant may comprise a compound having 4or more halides, 5 or more halides, or 6 or more halides, wherein thehalides can be, but are not limited to, chlorine and/or fluorine. Insome embodiments, the first reactant may comprise a —CF₃ group. In someembodiments, the first reactant may comprise a —CF₃ group that mayassist in selective etching. In some embodiments, the first reactant maycomprise a —CF₃ group and sulfur. In some embodiments, the firstreactant may comprise a —CF₃ group, nitrogen and oxygen. In someembodiments, the first reactant may comprise a —CF₃ group, carbon,hydrogen and oxygen, for example chlorodifluoroacetic acid. In someembodiments, the first reactant may comprise a —CF₃ group and a —NH₂group. In some embodiments, the first reactant may comprise a —CF₃group, a —NH₂ group and either oxygen or sulfur.

In some embodiments, the first reactant may comprise a —CF₃ group,oxygen and nitrogen, and may be connected via hydrocarbon chain, such asan alkyl chain. In some embodiments, the first reactant may comprise 1or more CX_(a)Y_(b)— groups, wherein X and Y are halides and can be, butare not limited to, fluorine and/or chlorine. In some embodiments, thefirst reactant may also comprise carbon, hydrogen and oxygen, forexample chlorodifluoroacetic anhydride. In some embodiments, the firstreactant may comprise HCl or HF, for example as a stabilizer, when thefirst reactant is not in vaporized form in the reactant source vessel.In some embodiments, the first reactant may comprise HCl, which issupplied separately to the reaction chamber.

In some embodiments, the first reactant may comprise carbon and ahalogen. In some embodiments, the first reactant may comprise a compoundof formula CX_(a)Y_(b), wherein a and b can be greater than or equal toone, for example, in some embodiments, a first reactant may compriseCCl₃Br, CCl₂Br₂. In some embodiments, the first reactant may comprise acompound of formula CHX_(a)Y_(b), wherein a and b can be greater than orequal to one, for example in some embodiments, a first reactant maycomprise CHCl₂Br, CHCl₃, CHCl₂Br or CHClBr₂.

In some embodiments, the first reactant may comprise a compound offormula MO_(c)X_(a)Y_(b), wherein c can be greater than zero, and a and,or b can be greater than or equal to one and can be greater than equalto zero, and M can be any transition metal. For example in someembodiments, M can be Rhenium, Niobium, tungsten, Titanium, vanadium,chromium, and wherein X and Y can be halide different from each other orX and Y can same halide. In some embodiments, the first reactant maycomprise a compound of formula MoOF₄, ReOF₄, WOF₄, ReOF₅, ReO₂F₂,ReO₂Cl₃, NbOF₃.

In some embodiments, the first reactant may comprise an electronegativeelement, such as a halide such as fluorine or chlorine, close to the oradjacent to the atom through which the reactant bonds to the surface.For example, in some embodiments, the first reactant may comprisehexafluoroacetylacetone (Hhfac) in which fluorine is close to the C═Ogroup through which the hfac bonds to the surface.

In some embodiments, the first reactant may comprise a halo-halogencompound having the general formula X_(a)Y_(b), wherein X and Y can bechlorine or fluorine or bromine or iodine, a and b are thestoichiometric coefficients, where each of a and b can be greater thanor equal to 1. In some embodiments, the first reactant may comprise ClF,BrCl, ClF₃, BrF₃, ClF₅, BrF₅, IF₅, IF₇, ICl₃, ICl₅ or ICl. In someembodiments, the first reactant may comprise a halogen and oxygen. Insome embodiments, the first reactant may comprise an oxyhalide havinggeneral formulae O_(b)X_(a) or O_(b)X_(a)Y_(c). In some embodiments, thefirst reactant may comprise more than one halogen and more than oneoxygen. In some embodiments, the first reactant may comprise OF₂, FClO₂,or FClO₃.

In some embodiments, the first reactant may comprise halogen, nitrogenand sulfur. In some embodiments, the first reactant may comprise, forexample, thiazyl chloride (NSCl). In some embodiments, the firstreactant may comprise a halogen, nitrogen, oxygen and sulfur. In someembodiments, the first reactant may comprise, for example, NSOCl.

In some embodiments, the first reactant may comprise a halogen,phosphorous and oxygen. In some embodiments, the first reactant maycomprise, for example, POCl₃.

In some embodiments, the first reactant may comprise a substituted alkylammonium hydroxide compound, or an alkyl amine compound. In someembodiments an alkyl ammonium halide or hydroxide compound is formed onthe surface. For example, in some embodiments, the first reactant maycomprise or form on the surface such as tetramethylammonium hydroxide,or tetramethylamine. In some embodiments, the first reactant maycomprise a secondary or tertiary alkylamine.

In some embodiments, the first reactant may comprise a boron halidecompound comprising an organic ligand. For example, in some embodiments,the first reactant may comprise a compound having the formulaBX_(n)L_(3-n), wherein L is an organic ligand, such as anacetylacetonato (acac) ligand, X is a halide, and n is 1 or 2. In someembodiments, the first reactant may comprise BF₂acac.

In some embodiments, the first reactant may comprise carbon, hydrogen,and, or tin. For example in some embodiments, a first reactant may becomprise of a hexamethylditin. In some embodiments, the first reactantmay comprise carbon, hydrogen, halide and tin. For example in someembodiments, a first reactant may be comprise of a trimethyltinbromide.

In some embodiments the first vapor-phase reactant comprises a firsthalide ligand and the second vapor-phase reactant comprises a secondhalide ligand. In some embodiments both the first and second vapor phasereactants comprise Cl. In some embodiments the second halide ligand isdifferent from the first halide ligand.

In some embodiments the first vapor-phase halide reactant may beinorganic. In some embodiments the first vapor-phase halide reactantdoes not comprise carbon or both C and H. In some embodiments the secondvapor-phase reactant may be inorganic. In some embodiments the secondvapor-phase reactant may not comprise carbon or both C and H.

In some embodiments the first vapor phase reactant and second vaporphase reactant comprise the same number of halide ligands. In someembodiments the first vapor phase reactant and the second vapor phasereactant comprise a different number of halides. In some embodiments thefirst vapor phase reactant comprises one, two, three, four, five or sixhalides, while the second vapor phase reactant separately comprises one,two, three, four, five or six halides.

In some embodiments the first and second vapor phase reactants bothcomprise the same halides. In some embodiments the first and secondvapor phase reactants comprise different halides.

In some embodiments the first vapor-phase halide reactant comprises one,two, three, four, five or six halides, which may all be the same halide,or may differ, and the second vapor-phase reactant comprises a differentnumber of halides from the first reactant. The halides in the secondreactant may be the same as or different from the halides in the firstreactant. In some embodiments the second vapor-phase reactant may beselected from the reactants described herein; that is, in someembodiments two (or more) different reactants referred to as ‘firstvapor-phase reactants’ can be used in a deposition cycle as first andsecond reactants.

In some embodiments the first vapor-phase halide reactant comprises fromtwo to six halides (or halogen atoms), for example chlorides orfluorides, while the second vapor-phase reactant comprises two to sixhalides (or halogen atoms). In some embodiments the first vapor-phasehalide reactant comprises from three to five halides (or halogen atoms),for example chlorides or fluorides, while the second vapor-phasereactant comprises three to five halides (or halogen atoms). The halidesin the second vapor phase reactant may be the same as or different fromthe halides in the first vapor phase reactant.

In some embodiments both the first and second vapor-phase halidereactants comprise from four to five halides (or halogen atoms), forexample chlorides or fluorides. The halides in the second vapor phasereactant may be the same as or different from the halide in the firstvapor phase reactant.

In some embodiments the first vapor-phase halide reactant is afluorinating or chlorinating agent while the second vapor phase reactantis a chlorinating or fluorinating agent. In some embodiments the firstvapor phase halide reactant is a fluorinating agent while the secondvapor phase reactant is a chlorinating agent. In some embodiments thefirst vapor phase reactant is a chlorinating agent while the secondvapor phase reactant is a fluorinating agent.

In some embodiments the first vapor-phase halide reactant comprises morethan one, such as two or more, three or more, four or more or five ormore halides (or halogen atoms), for example chlorides or fluorides,while the second vapor-phase reactant comprises less than five, lessthan four, less than three or less than two halides (or halogen atoms).The halides in the second vapor phase reactant may be the same as ordifferent from the halides in the first vapor phase reactant.

In some embodiments the first vapor-phase halide reactant comprises fromfour to five halides (or halogen atoms), for example chlorides orfluorides, while the second vapor-phase reactant comprises less thanfive, less than four, less than three or less than two halides (orhalogen atoms). The halides in the second vapor phase reactant may bethe same as or different from the halides in the first vapor phasereactant.

In some embodiments the second vapor-phase halide reactant comprisesmore than one, such as two or more, three or more, four or more or fiveor more halides (or halogen atoms), for example chlorides or fluorides,while the first vapor-phase reactant comprises less than five, less thanfour, less than three or less than two halides (or halogen atoms). Thehalides in the second vapor phase reactant may be the same as ordifferent from the halides in the first vapor phase reactant.

In some embodiments the second vapor-phase halide reactant comprisesfrom four to five halides (or halogen atoms), for example chlorides orfluorides, while the first vapor-phase reactant comprises less thanfive, less than four, less than three or less than two halides (orhalogen atoms). The halides in the second vapor phase reactant may bethe same as or different from the halide in the first vapor phasereactant.

In some embodiments, the first non-metal halide reactant is a non-metalhalide reactant with the formula Ligand-SX₂ as well as Ligand-SX₃, whereX is a halide and S can be sulfur and phosphor, Ligand can bedialkylether like dimethylether, dialkylthioether likedi-methylthioether, alkylamines like dimethylamine, benzene, alkyl,pyridine, thiophene, cyclopropane and n-haloiminosulfur etc. In someembodiments, the first vapor-phase non-metal halide reactant can betrifluoro(N-methylmethanaminato)sulfur. In some embodiments, the firstvapor-phase non-metal halide reactant is a N-FluoroformyliminosulfurDifluoride (SF2=NCOF).

In some embodiments, a halide reactant, such as fluoride, chloride,bromide or iodide is used as the second reactant that reacts with theadsorbed species to form volatile reaction products that can be removedfrom the reaction space. In some embodiments, the second reactant is anon-metal or semi-metal halide. For example, in some embodiments, thesecond reactant is carbon based halide. In some embodiments, the secondreactant may comprise, for example, carbon based fluoride, bromide,iodide or chloride, for example, CCl₄ or CBr₄. In some embodiments, thesecond reactant is a semimetal based halide, such as a Ge halide, forexample a semimetal chloride, like SbCl₃, SbCl₅, SiCl₄, or GeCl₄. Insome embodiments, any of the reactants described above with reference tothe first reactant may be used as the second reactant along with any ofthe above-described first reactants. That is, any two of theabove-described first reactants may be used as a first reactant and asecond reactant. For simplicity reasons, carbon based halide, includingCCl₄, is considered to be organic or alkylhalide.

In some embodiments, the second reactant may comprise a compound capableof forming volatile adducts on a surface or substrate that has beencontacted with a first reactant as described herein. The second reactantforms volatile adducts with the species formed on the substrate surfaceby the first reactant, and the adducts include one or more atoms fromthe surface to be etched. The volatile adducts may then be removed fromthe reaction space. For example, in some embodiments, the secondreactant may comprise a compound capable of forming a volatile adduct ona contact with surfaces such as —OH, —SH, —NH2, ═NH terminated as wellas halidized surface, such as a chlorinated high-k surface, or on anoxidized surface, or an amine coordinated surface.

In some embodiments, the second reactant may comprise a compound capableof forming a metal halide adducted compound on a surface that has beencontacted with a first reactant as described herein.

In some embodiments, the second reactant may comprise a compound capableof forming coordinated bonds to a metal atom that has adsorbed to thesubstrate surface. For example, diamines, dithiones, thiocarbonates,thiadiazoles can form coordinated bonds to the metal atoms on thesurface.

In some embodiments, the second reactant may comprise a Lewis base thatwill form volatile adducts on reaction with metals on the surface to beetched, such as transition metals. For example, in some embodiments, thesecond reactant may comprise pyridine, tetrahydrofuran (THF), dimethylsulfoxide (DMSO), tetrahydrothiophene, or other Lewis bases which mayform volatile adducts on the surface. In some embodiments, Lewis basesinclude alkyl or aryl or substituted nitriles (cyanates) and isonitrileslike methyl nitrile, methyl isonitrile, NH₃ gas, alkyl or substitutedisothiocyanates, isocyanates, poly-ols (such as propane 1,2,3 ols),ethanolamine, sulfones (such as methylsulfonylmethane), PX₃ andtrichloronitromethane.

In some embodiments where the material being etched comprises a metalnitride, such as TiN or TaN, the second reactant may comprise a Lewisacid. In some embodiments, the Lewis acid is SO₃. In some embodiments,the second reactant may comprise planar compounds such as BCl₃, BF₃, orAlCl₃, a compound having a conjugated electron system, or a hypervalentmolecule that will form adducts on the surface to be etched.

In some embodiments, the second reactant may comprise a diamine ordithione compound that will form adducts on the surface to be etched.

In some embodiments, the second reactant may comprise an alkyl or arylisocyanates, or their substituted forms that can also form adducts onsubstrate surfaces to be etched, such as surfaces comprising transitionmetals. In some embodiments, the second reactant may comprise an alkylor aryl isothiocyanate, or their substituted form.

In some embodiments, the volatile adduct forming second reactant maycomprise alkyl or aryl poly-ols, for example 1,2,3, propane triol andethane diol etc.

In some embodiments, adduct forming second reactant may comprise —NH₂and —OH functional groups, for example ethanolamine.

In some embodiments, adduct forming second reactant may comprise sulfurtrioxide (SO₃),

In some embodiments second reactant may comprise sulfones like, forexample, methylsulfonylmethane, which can assist in forming volatileadducts.

In some embodiments, the second reactant may comprise a heterocyclicreactive compound. In some embodiments, the second reactant may comprisea heterocyclic reactive compound containing more than equal to oneNitrogen atoms. In some embodiments, the second reactant may comprise aheterocyclic reactive compound containing more than equal to one Sulfuratoms. In some embodiments, the second reactant may comprise aheterocyclic reactive compound containing more than equal to one Oxygenatoms. In some embodiments, the second reactant may comprise aheterocyclic reactive compound containing more than two different atomssuch as Oxygen, Boron, Nitrogen and Sulfur atoms. For example, in someembodiments, the second reactant may comprise a thiocarbonate compound,such as ethylene trithiocarbonate or dimethyl trithiocarbonate. In someembodiments, the second reactant may comprise a thiadizole compound,such as dicholor-thiadiazole, for example 3,4 dichloro-1,2,5thiadiazole. In some embodiments, the second reactant may comprise adioxane compound, such as 1,4-dioxane. In some embodiments, the secondreactant may comprise a substituted or unsubstituted unsaturated cycliccompound comprising cyclohexadiene, cyclopentadine, such astrans-tris(trimethylsilyl)cyclohexadiene andbis(trimethylsilyl)cyclohexadiene.

In some embodiments, the second reactant may comprise a compound capableof forming an atrane compound when contacting a surface that has beenexposed to a first reactant as described herein. For example, in someembodiments, the second reactant may comprise TIPA, TIPEA, TMEA,tris(2-aminoethyl)amine or triethanolamine (TEA), which may formvolatile adducts such as metal atrane compounds when contacting asurface that has been exposed to a first reactant, such as a first metalhalide reactant, as described herein.

In some embodiments, a metal film, such as a transition metal film isetched by an ALE process comprising exposing the substrate to a firsthalide reactant, such as a metal halide like NbCl₅, and a secondvolatile adduct-forming reactant, such as CS₂. In some embodiments, CS₂can be used on a halidized surface such as HfCl_(x), TiCl_(x), orTiONCl_(x) to form volatile products

The substrate surface to be etched is alternately contacted with thefirst reactant and second reactant and volatile adducts and reactionbyproducts are removed, thereby etching the transition metal film. Inone embodiment TiN can be etched by an ALE process comprisingalternately exposing the substrate to chlorine containing compound suchas NbCl₅ and adduct forming compound such as CS₂.

In some embodiments a metal surface such as an Fe, Co, Ni, or Cu surfaceis halidized by exposure to a first halide reactant. The surface is thenexposed to a second reactant that forms a volatile metal adduct andthereby etches the surface.

In some embodiments a metal oxide film on a substrate is etched by anALE process comprising an etch cycle in which the metal oxide film isalternately exposed to a first halide reactant, such as a metal halideor CCl₄ and a second volatile adduct forming reactant, such as CH₃CN,NH₃ or 1,4-dioxane. In some embodiments Al₂O₃, HfO₂, TiO₂ or other metaloxide film on a substrate surface is etched by alternate exposure to afirst reactant comprising a metal halide or CCl₄ and a second reactantcomprising 1,4-dioxane.

In some embodiments, the second reactant, such as CCl₄, can be usedalone, without a first reactant and can provide the desired controlledetching with the desired etch selectivity.

In some embodiments, the first reactant or the second reactant can beused alone for the etching and can provide the desired controlledetching with the desired etch selectivity. Any by-products that areformed may be removed by purging and/or by pumping.

In some embodiments the first reactant alone can be used in cyclicpulsing fashion.

In some embodiments, a continuous flow of the first reactant with flowrate modification, or “pulsing” of flow rate, is used.

In some embodiments, the first and the second reactants can be usedinterchangeably for the desired controlled etching with the desired etchselectivity.

In some embodiments two or more compounds described herein as firstreactants can be used in cyclic fashion in an atomic layer etchingprocess. For example, in some embodiments, the first reactant is NbF₅and the second reactant is fumaryl chloride or malonyl or any acylhalide.

In some embodiments, the first reactant is NbF₅ and the second reactantis CCl₄.

In some embodiments, the first reactant and the second reactant comprisethe same halide ligand. For example, the first reactant may comprise ametal chloride, such as NbCl₅, TaCl₅, MoCl₃ or WCl₂ and the secondreactant may also comprise Cl, such as CCl₄.

In some embodiments either or both of the first or second reactantcomprises a halide and does not contain hydrogen, or comprises a halideand does not contain either oxygen or hydrogen. In some embodimentseither the first or second reactant comprises a halide but does notcontain hydrogen, or comprise a halide but not contain either oxygen orhydrogen. In some embodiments at least one of the first and secondreactants is not Sn(acac)₂. In some embodiments at least one of thefirst and second reactants is not TMA. In some embodiments at least oneof the first and second reactants is not HF gas. In some embodiments atleast one of the first and second reactants is not HF-Pyridine. In someembodiments the first and second reactants are not HF and Sn(acac)₂. Insome embodiments the first and second reactants are not HF and SiCl₄. Insome embodiments, H is not used. In some embodiments, TMA is not used.In some embodiments Sn(acac)₂ is not used.

In some embodiments, one or more additional reactants may be utilized.In some embodiments, one or more reactants may be used to improve ortune selective etching. The additional reactants may be providedseparately, or may be combined with one or more reactants, such as withthe second reactant. In some embodiments, the additional reactant may bean oxygen source. For example, the additional reactants may comprise,for example, water, oxygen or ozone.

In some embodiments, water, oxygen and/or ozone is combined with thesecond reactant. The ratio of water, oxygen or ozone to the secondreactant may be varied to tune the reaction, for example to tune theselectivity of the etch process or even to stop the etching by formingan etch-stop layer.

In some embodiments, the additional reactant may comprise SO₃, H₂S, NH₃,hydrazine, where a and b are greater than zero. In some embodiments, theadditional reactant may be used in combination with other first and/orsecond reactants.

In some embodiments, an additional reactant may be a N₂O gas. Theadditional reactant may be supplied additionally from a separate source.

In some embodiments, an etch cycle additionally comprises a phase inwhich the substrate is exposed to a ligand exchanger. In someembodiments, the ligand exchanger is selected from Hacac TMA, Sn(acac)₂.In some embodiments, the ligand exchanger may consists of vicinal ketonegroups for example hexafluoro acetylacetonato (Hhfac), diacetyl, thdetc. In Some embodiments a ligand exchanger consists of M(thd)xcompound, wherein M is metal like transition metals as well as alkalineearth metals and x can be greater than 1 and in some cases greater than2. In some embodiments Metal ‘M’ can consists of at least one ‘thd’ andor at least one ‘acac’ or both, for example Mg(thd)(acac) etc.

As mentioned above, in some embodiments the ALE process is preferably athermal process. Thus, in some embodiments a plasma reactant is not usedas a first or second reactant. In some embodiments a plasma reactant isnot used in the ALE process.

In some embodiments for controlled etching, one or more ALE cycles arecarried out, with each cycle removing material from the desiredsubstrate surface. In some embodiments, up to a monolayer of material isremoved in each ALE cycle, where the mass removed per cycle is about amonolayer of volume, assuming density does not change. In someembodiments, more than a monolayer per cycle is removed. Each ALE cycletypically comprises at least two distinct phases. The contacting of thesubstrate surface and removal of a reactant from the substrate may beconsidered a phase.

In a first phase, a vapor phase first reactant contacts the substratesurface to be etched. In some embodiments, the first reactant forms nomore than about one monolayer of adsorbed species. In particular, insome embodiments, the first reactant reacts with accessible substratemolecules of the material to be removed on the substrate surface to formthe adsorbed species.

The first phase is self-limiting in some embodiments. In some instancesit may be the case that limited availability of substrate surfacemolecules to react with the vapor phase first reactant species ensuresthat the reaction is essentially self-limiting. In addition, the formedreaction layer itself can introduce self-limiting behavior.

In some embodiments, excess first vapor phase reactant and any reactionbyproducts are removed from the proximity of the substrate surface. Thefirst vapor phase reactant and any reaction byproducts may be removedfrom proximity of the substrate surface with the aid of a purge gasand/or vacuum. In some embodiments, excess reactant and/or reactantbyproducts are removed from the reaction space by purging, for examplewith an inert gas. In some embodiments, the substrate may be moved inorder to facilitate removal of the reactant and/or reactant byproductsfrom the vicinity of the substrate, for example by moving the substrateto a different reaction chamber.

In a second phase, a second vapor phase halide reactant contacts thesubstrate and may convert adsorbed species to vapor phase reactionproducts. The reaction products include atoms of the original material,thus etching the material. In some embodiments, the second reactantcomprises the same halide as the first reactant. In some embodiments,the second reactant does not comprise a reactive species. Excess secondreactant and vapor phase reaction products are removed from thesubstrate surface, for example with the aid of vacuum and/or a purgegas. In some embodiments, excess second reactant and reaction byproductsare removed from the reaction space by purging, for example with aninert gas. In some embodiments, the substrate may be moved in order tofacilitate removal of the reactant and/or reaction byproducts from thevicinity of the substrate, for example by moving the substrate to adifferent reaction chamber.

Additional phases may be added and phases may be removed as desired toadjust the etch rate and/or to influence one or more properties of theremaining film after etching film, such as tune the resistivity, forexample decrease or increase the resistivity on post etching by factoror 1% or more than 5% or more than 20% or more than 50% or more than100%, modify optical properties for example decrease or increase theoptical parameters like (n,k) on post etching by factor or 1% or morethan 5% or more than 20% or more than 50% or more than 100%, modify thefilm roughness for example decrease or increase the roughness on postetching by factor or 1% or more than 5% or more than 20% or more than50% or more than 100%, and improve the selectivity of etching forexample decrease or increase the selectivity on post etching by factoror 1% or more than 5% or more than 20% or more than 50% or more than100%. In some embodiments, the second reactant, such as CCl₄, can beused alone, without a first reactant and can provide the desiredcontrolled etching with the desired etch selectivity. In someembodiments, one or more additional reactants may be provided in aseparate phase, such as an oxygen reactant like oxygen, water or ozone.

In some embodiments, a third phase is added by depositing a thirdvapor-phase reactant. The third phase may then be removed to adjust theetch rate and/or to influence the etched material. A fourth phase isadded by depositing a fourth vapor-phase reactant. And additional phasesare added by depositing additional vapor-phase reactants.

One or more of the reactants may be provided with the aid of a carriergas, such as Ar or He. In some embodiments, the first reactant and thesecond reactant are provided with the aid of a carrier gas. In someembodiments, the carrier gas may flow continuously throughout theprocess. In some embodiments, the carrier gas may also serve as a purgegas.

The first and second phases together form an ALE etching cycle thatcontrollably removes material from the substrate surface. The ALEetching cycle may be repeated two or more times to etch the material onthe substrate surface to a desired degree. In some embodiments, the ALEetching cycle is repeated 10, 20, 50, 100, 200, 400, 600, 800, 1000 ormore times to remove the desired amount of material.

In some embodiments, two of the phases may overlap, or be combined. Forexample, the first reactant and the second reactant may contact thesubstrate simultaneously in phases that partially or completely overlap.In addition, although referred to as the first and second phases, andthe first and second reactants, the order of the phases may be varied,and an ALE cycle may begin with any one of the phases.

Due to the use of vapor phase reactants, the conformality of the etchingprocess is very good, and material can be removed evenly from allsurfaces of a three-dimensional structure. In some embodiments, theconformality of etching vertically is greater than about 90% and theconformality of etching horizontally is greater than about 92%. In someembodiments conformality of etching in vertical openings is about 50% orgreater, about 75% or greater, about 85% or greater, about 90% orgreater, about 95% or greater, about 98% or greater, about 99% orgreater, and even up to about 100%. In some embodiments conformality ofetching in openings extending horizontally (for example from verticalopenings), is about 50% or greater, about 75% or greater, about 85% orgreater, about 90% or greater, about 95% or greater, about 98% orgreater, about 99% or greater, and even up to about 100%. In someembodiments, the process comprises more than two phase, more than threephases or more than four phases or more than five phases applied incyclic manner.

In some embodiments, the substrate comprising a material to be etched,such as a semiconductor workpiece, is loaded into a reaction space orreactor. The reactor may be part of a cluster tool in which a variety ofdifferent processes in the formation of an integrated circuit arecarried out. In some embodiments, a flow-type reactor is utilized. Insome embodiments, a shower head type of reactor is utilized. In someembodiments, a space divided reactor is utilized. In some embodiments, ahigh-volume manufacturing-capable single wafer atomic layer depositionreactor is used. In other embodiments a batch reactor comprisingmultiple substrates is used.

Examples of suitable reactors that may be used include commerciallyavailable equipment such as the F-120® reactor, F-450® reactor, Pulsar®reactors—such as the Pulsar® 2000 and the Pulsar® 3000—EmerALD® reactorand Advance® 400 Series reactors, available from ASM America, Inc ofPhoenix, Ariz. and ASM Europe B.V., Almere, Netherlands. Othercommercially available reactors include those from ASM Japan K.K (Tokyo,Japan) under the tradename Eagle® XP and XP8. In some embodiments, thereactor is an etch reactor.

In some embodiments, if necessary, the exposed surfaces of the workpiececan be pretreated to provide reactive sites to react with the firstphase of the ALE process. In some embodiments, a separate pretreatmentstep is not required. In some embodiments, the substrate is pretreatedto provide a desired surface termination. In some embodiments, thesubstrate is pretreated with plasma.

The reactants, such as the first reactant and second reactant, aresupplied to the reaction space in gaseous form. The first reactant andsecond reactant gas are considered “volatile” for purposes of thepresent description if the species exhibits sufficient vapor pressureunder the process conditions to transport the species to the workpiecein sufficient concentration to saturate exposed surfaces.

In some embodiments, a reactant is pulsed into the reaction chambercontaining the substrate with the surface to be etched for about 0.01 toabout 60 seconds, about 0.05 to about 30 seconds, about 0.05 seconds toabout 5.0 seconds, about 0.1 seconds to about 3 seconds or about 0.2seconds to about 1.0 seconds. In some embodiments, the pulse time may begreater than 60 seconds, for example up to 120 seconds or more. In someembodiments, the reactant contacts the substrate surface to be etchedfor about 0.01 to about 60 seconds, about 0.05 to about 30 seconds,about 0.05 seconds to about 5.0 seconds, about 0.1 seconds to about 3seconds or about 0.2 seconds to about 1.0 seconds. In some embodiments,the pulse time may be greater than 60 seconds, for example up to 120seconds. The optimum time can be readily determined by the skilledartisan based on the particular circumstances.

As mentioned above, after sufficient time for about a molecular layer toreact with the material to be removed on the substrate surface and formthe adsorbed species, excess first reactant, and reaction byproducts, ifany, are removed from the substrate surface. In some embodimentsremoving excess reactant and reaction byproducts, if any, may comprisepurging the reaction chamber. In some embodiments, the reaction chambermay be purged by stopping the flow of the first reactant whilecontinuing to flow a carrier gas or purge gas for a sufficient time todiffuse or purge excess reactants and reactant by-products, if any, fromthe reaction space. Reaction by-products may comprise, for example,oxyhalides. In some embodiments, the excess first reactant is purgedwith the aid of inert gas, such as helium or argon, which is flowingthroughout the ALE cycle. In some embodiments, the substrate may bemoved from the reaction space containing the first reactant to a second,different reaction space. In some embodiments, the first reactant isremoved for about 0.01 to about 60 seconds, 0.05 to about 30 seconds,about 0.1 seconds to about 10 seconds, about 0.3 seconds to about 5seconds or about 0.3 seconds to about 1 second. In some embodiments itmay be 60 seconds or more.

In the second phase, the second reactant, such as CCl₄, is provided tothe workpiece. Typically the second reactant is pulsed into the reactionchamber containing the substrate with the surface to be etched for about0.01 to about 60 seconds, about 0.05 to about 30 seconds, about 0.05seconds to about 5.0 seconds, about 0.1 seconds to about 3 seconds orabout 0.2 seconds to about 1.0 seconds. In some embodiments, the secondreactant contacts the substrate surface to be etched for about 0.05seconds to about 5.0 seconds, about 0.1 seconds to about 3 seconds orabout 0.2 seconds to about 1.0 seconds. In some embodiments, the pulsemay be greater than about 60 seconds. However, depending on the reactortype, material being etched and other process conditions, such assurface area and temperature, the second reactant contacting time may beeven higher than about 10 seconds. In some embodiments, contacting timescan be on the order of minutes. The optimum contacting time can bereadily determined by the skilled artisan based on the particularcircumstances.

The second reactant reacts with the adsorbed species to form vapor phasereaction by-products that include atoms of the material being etched.Excess second reactant and the vapor phase reaction by-products areremoved from the reaction chamber. In some embodiments removing excessreactant and reaction byproducts may comprise purging the reactionchamber. In some embodiments, the reaction chamber may be purged bystopping the flow of the second reactant while continuing to flow acarrier gas or purge gas for a sufficient time to diffuse or purgeexcess reactants and reactant by-products, from the reaction space. Insome embodiments, the excess second reactant and reaction by-productsare purged with the aid of inert gas, such as helium or argon. In someembodiments, the substrate may be moved from the reaction spacecontaining the second reactant to a different reaction space. The pulseof purge gas may, in some embodiments, be from about 0.1 seconds toabout 10 seconds, about 0.1 seconds to about 4 seconds or about 0.1seconds to about 0.5 seconds.

According to some embodiments, the ALE cycles may be performed attemperatures ranging from about 20 to about 1200° C., about 50 to about800° C., about 75 to about 600° C., about 300° C. to about 500° C., orfrom about 350° C. to about 450° C. In some embodiments, the temperatureis greater than about 20, 50 or 100° C., but less than about 1000, 800,600 or 500° C. In some embodiments, the cycles are carried out at atemperature of about 450° C.

The pressure in the reaction chamber is typically from about 10E-9 torrto about 760 torr, or about 0.001 to about 100 torr. However, in somecases the pressure will be higher or lower than this range, as can bedetermined by the skilled artisan given the particular circumstances. Insome cases the reactor can be operated either in isothermal (such ashot-wall) or non-isothermal (such as cold-wall) conditions. In somecases reactor does not interact with etching chemistries and may alsonot interact with substrates. In some cases reactor can be hot-wall,cold and even warm-wall type of reaction chamber.

The substrate comprising a material to be etched, also referred to astarget material, can take a variety of forms. In some embodiments, thesubstrate may be an integrated circuit workpiece or other substrate. Thetarget material to be etched may comprise a thin film on the substratesurface. In some embodiments, the target material is a thin film on athree-dimensional structure on a substrate. The substrate comprising athin film or other material to be etched may comprise various types ofother materials. For example, in some embodiments, the substrate maycomprise silicon in addition to a material that is targeted by theetching process. In some embodiments, the etch process is selectiverelative to other materials on the substrate or in the reaction chamber.In some embodiments either first reactant alone, or second reactantalone, or first as well as second reactant is supplied in a cyclicfashion to improve the selectivity.

In some embodiments, the target material to be etched comprises a metal,such as Jr, Ru, Rh, Mo, Cu, Sb, Al, Ti, Co, Ni, Ta, Al, Zr, Hf, or W. Insome embodiments, the material to be etched comprises one or more of W,WO₃, AlN, TiN, TiO₂, GaN, MoN, CoP, TaN, SiN, SiO_(x), AlO_(x), AlO₂,Al₂O₃, ZrO_(x), ZrO₂, and HfO_(x), for example HfO₂. In someembodiments, the material to be etched comprises metal nitride or metaloxide or mixtures thereof.

In some embodiments, a thin film comprising one or more of W, TiN, TiO₂,TaN, SiN, SiO_(X), AlO_(x), AlO₂, Al₂O₃, ZrO_(x), ZrO₂, WO₃, AlN,HfO_(x) and HfO₂ is etched by an ALE process comprising alternately andsequentially contacting a substrate comprising the thin film with NbF₅and CCl₄. In some embodiments, a thin film comprising one or more of W,TiN, TiO₂, TaN, SiN, SiO_(X), AlO_(x), AlO₂, Al₂O₃, ZrO_(x), ZrO₂, WO₃,AlN, HfO_(x) and HfO₂ is etched by an ALE process comprising alternatelyand sequentially contacting a substrate comprising the thin film with afirst reactant and a second reactant, wherein the first reactant and thesecond reactant comprise the same halide.

In some embodiments, the ALE process has an average etch rate of about0.01 to about 5 Å/cycle. Etch rate is defined as amount of material orthickness of film is removed after each cycle, for practical reasons itcan be calculated after 1 etching cycles or more than 2 etching cyclesor more than 5 or even higher than 20 or sometimes higher than 50cycles. In some embodiments, the average etch rate is about 0.01 to 0.1Å/cycle or from 0.1 to about 2 Å/cycle or in some cases even higher than2 Å/cycle. In some embodiments, the average etch rate is more than about0.1 Å/cycle, more than about 0.5 Å/cycle, more than about 1.0 Å/cycle,more than about 2.0 Å/cycle, more than about 3.0 Å/cycle, more thanabout 5.0 Å/cycle, more than about 10 Å/cycle or more than about 20Å/cycle and in some instances if continuous flow is applied with flowrate modification or the exposure times are long enough the etch ratescan be more than about 30 Å/cycle, more than about 50 Å/cycle or morethan about 100 Å/cycle.

In some embodiments the etch selectivity i.e. the ratio of material(thickness, mass or amount of atoms/molecules) removed from the desiredsurface/material to material removed from the non-desiredsurface/materials or surfaces/materials, is from more than about 2:1,more than about 3:1, more than about 5:1, more than about 7:1, more thanabout 10:1, more than about 15:1, more than about 20:1, more than about30:1, more than about 50:1, more than about 100:1, more than about1000:1. In some embodiments no substantial amount of material is removedfrom the non-desired surface/material.

In some embodiments the flow or first or second reactant can be higherthan 2 sccm, can be greater than 10 sccm or sometimes even higher than50 sccm or can be more than 100 sccm or more than 500 sccm etc. In someembodiments first reactant can be continuously flown into the reactionchamber while second reactant is flown intermittently.

FIG. 1 is a flow chart that depicts an embodiment of an ALE methodgenerally. The ALE method depicted in FIG. 1 comprises a first exposingstep 100, a first removing step 110, a second exposing step 120, and asecond removing step 130.

In some embodiments, a substrate having an etch target material isplaced in a reaction chamber and exposed to a first vapor-phase reactantin the first exposing step 100. The etching target is typically exposedto the first vapor-phase reactant for a period of time as providedabove. In some embodiments, the pulse time is about 0.1 to 10 seconds,or 0.1 to 5 seconds.

After the first exposing step 100, excess first vapor-phase reactant isremoved from the reaction chamber in the first removing step 110. Thereaction chamber may be evacuated with a vacuum pump and or/by replacingthe gas inside the reactor with an inert gas such as argon or nitrogen.The removing step 110 may typically take about 0.05 to 20 seconds.However, the removing step may take more or less time if necessary.

The substrate is subsequently be exposed to a second vapor-phasereactant in the second exposing step 120. The second reactant may be thesame as the first vapor-phase reactant. The etching target is typicallyexposed to the second vapor-phase reactant for a period of time asdiscussed above, for example about 0.1 seconds to 10 seconds.

After the second exposing step 120, excess second vapor-phase halidereactant and volatile reaction byproducts are removed from the reactionchamber in the second removing step 130. In some embodiments, the firstexposing step 100, the first removing process 110, the second exposingstep 120, and the second removing step 130 form an ALE etch cycle 150that may be repeated until a desired amount of etching of the targetmaterial is obtained. In some embodiments, the first exposing step 100,the first removing process 110, the second exposing step 120, and thesecond removing step 130 may be repeated for 10, 20, 50, 100, 200, 500,1000 or more cycles.

In some embodiments, the etch target material comprise of metals like W,Pt, Cu, Ni, Co, Ti, Zn, Nb, Mo, Ta etc. In some embodiments, the etchtarget material comprise of metal nitrides, for example MoN, NbN, SiN,TiN, TaN, WN, AlN etc. In some embodiments, the etch target materialcomprise of carbides like SiC, TiC, TaC, AlC, HfC, MoC, NbC etc. In someembodiments, the etch target material comprise of oxides, such asdielectric oxides, for example AlOx, ZrOx, HfOx, TiOx, TaOx, NbOx, MoOx,SiOx, LaOx etc. In some embodiments, the etch target material compriseof 2D materials and/or sulfides like WS2, MoS2, TiS2, SnS2 etc. In someembodiments, the etch target material comprise of metal oxy nitrideslike TiONx, metal carbonitrides, such as WNC, oxycarbides e.g. andelemental substrates like Si, C, a-C, graphene etc.

In some embodiments, the first reactant comprises Nb, Ta, Mo or W.

Referring to FIG. 2, according to some embodiments an etch target thinfilm comprising W, TiN, TiO₂, TaN, SiN, SiO_(X), AlO_(x), AlO₂, Al₂O₃,ZrO_(x), ZrO₂, WO₃, AlN, HfO_(x) or HfO₂ on a substrate in a reactionspace is etched by an ALE process comprising at least one etch cycle 240comprising: contacting the substrate with a vapor phase metal chloridereactant that does not comprise excited species at step 200 such thatthe metal chloride reactant reacts with the thin film on the surface ofthe substrate to form adsorbed species; removing excess metal chloridereactant and reaction byproducts, if any, from the substrate surface atstep 210; contacting the substrate with a second chloride reactant thatdoes not comprise reactive species at step 220 thereby converting theadsorbed species into vapor phase reaction by-products that includeatoms of the etch target thin film; removing excess second chloridereactant and reaction byproducts, if any, from the substrate surface atstep 230; and optionally repeating the contacting and removing steps atstep 240 to etch the etch target thin film to a desired extent.

Referring to FIG. 3, according to some embodiments an etch target thinfilm comprising W, TiN, TiO₂, SiOC, SICN, SiOCN, SiON, TaN, SiN,SiO_(X), AlO_(x), AlO₂, Al₂O₃, ZrO_(x), ZrO₂, WO₃, AlN, HfO_(x) or HfO₂on a substrate in a reaction space is etched by an ALE processcomprising at least one etch cycle 340 comprising: contacting thesubstrate with vapor phase NbF₅ at step 300; removing excess NbF₅ andreaction byproducts, if any, from the substrate surface at step 310;contacting the substrate with vapor phase CCl₄ at step 320; removingexcess CCl₄ and reaction byproducts from the substrate surface at step330; and optionally repeating the contacting and removing steps at step340 to etch the etch target thin film to a desired extent.

Referring to FIG. 4, according to some embodiments an etch target thinfilm comprising W, TiN, TiO₂, TaN, SiN, SiO_(X), AlO_(x), AlO₂, Al₂O₃,ZrO_(x), ZrO₂, WO₃, AlN, HfO_(x) or HfO₂ on a substrate in a reactionspace is etched by an ALE process comprising at least one etch cycle 440comprising: contacting the substrate with a vapor phase metal halidereactant that does not comprise excited species at step 400 such thatthe metal halide reactant reacts with the thin film on the surface ofthe substrate to form adsorbed species; removing excess metal halidereactant and reaction byproducts, if any, from the substrate surface atstep 410; contacting the substrate with a second organic reactant thatdoes not comprise reactive species at step 420 thereby converting theadsorbed species into vapor phase reaction by-products that includeatoms of the etch target thin film; removing excess second organicreactant and reaction byproducts, if any, from the substrate surface atstep 430; and optionally repeating the contacting and removing steps atstep 440 to etch the etch target thin film to a desired extent.

Referring to FIG. 5, according to some embodiments an etch target thinfilm comprising W, TiN, TiO₂, TaN, SiN, SiO_(X), AlO_(x), AlO₂, Al₂O₃,ZrO_(x), ZrO₂, WO₃, AlN, HfO_(x) or HfO₂ on a substrate in a reactionspace is etched by an ALE process comprising at least one etch cycle 540comprising: contacting the substrate with a vapor phase metal halidereactant that does not comprise excited species at step 500 such thatthe metal halide reactant reacts with the thin film on the surface ofthe substrate to form adsorbed species; removing excess metal halidereactant and reaction byproducts, if any, from the substrate surface atstep 510; contacting the substrate with a second adduct forming reactantthat does not comprise reactive species at step 520 thereby convertingthe adsorbed species into volatile adducts that include atoms of theetch target thin film; removing excess second adduct forming reactantand reaction byproducts, if any, from the substrate surface at step 530;and optionally repeating the contacting and removing steps at step 440to etch the etch target thin film to a desired extent.

According to some embodiments an etch target thin film comprising Al₂O₃,HfO₂, TiO₂ or another metal oxides on a substrate in a reaction space isetched by an ALE process comprising at least one etch cycle comprising:contacting the substrate with a first vapor phase reactant comprising ametal halide or CCl₄ that does not comprise excited species such thatthe first reactant reacts with the thin film on the surface of thesubstrate to form adsorbed species; removing excess first reactant andreaction byproducts, if any, from the substrate surface; contacting thesubstrate with a second organic reactant comprising 1,4-dioxane thatdoes not comprise reactive species thereby converting the adsorbedspecies into volatile adducts that include atoms of the etch target thinfilm; removing excess second organic reactant and reaction byproducts,if any, from the substrate surface; and optionally repeating thecontacting and removing steps to etch the etch target thin film to adesired extent.

EXAMPLES

Thermal ALE was used to etch thin films of SiO₂ (thermal and native),TiN, TiO_(x), TaN, AlO_(x), AlN, ZrO_(x) and HfO_(x). The ALE cyclecomprised alternate and sequentially contacting a substrate comprisingthe relevant film with NbF₅ and CCl₄; NbF₅ and a mixture of CCl₄ andH₂O; NbF₅ and a mixture of CCl₄ and O₃; or CCl₄ alone. As shown in Table1 below, etching of each of the various types of thin films wasobserved, with the etch rate ranging from about 0.1 Å/cycle to about 1.8Å/cycle. No etching of SiO₂ films or SiO_(x) or SiN_(x) was observed.

TABLE 1 Reactant Reactant T_(reac.) Etch rate (Å/cycle) 1 2 ° C. TiNTiOx TaN AlOx AlN ZrOx HfOx NbF₅ CCl₄ 458 ~0.2 1.8 Yes 0.1-1.6 Yes 0.40.1-1.8 (0.5) NbF₅ CCl₄ + 458 Yes Yes Bulk Yes Yes Yes Yes H₂O rem. NbF₅CCl₄ + 458 Yes Yes Bulk Yes Yes Yes Yes O₃ rem. CCl₄ 458 0.1 — 0.4 No —No No — Not tested

FIG. 6 is a graph showing the differences of mass, thickness, and sheetresistance of SiO₂, TiN, TiO₂, SiN, TaN, ZrO₂, and Al₂O₃ after thermalALE processing. Substrates comprising thin films of each material wereplaced in a Pulsar 2000™ reactant. The thermal ALE cycle comprisedalternate and sequential pulses of NbF₅ and CCl₄. The substratetemperature was about 450° C. (susceptor temperature of 465° C. and topplate temperature of 405° C.). Mass, thickness and sheet resistance weremeasured after 1000 ALE cycles for the SiO₂, Tin, TiO₂, SiN, and TaNfilms and after 100 cycles for ZrO₂, Al₂O₃ and TiO₂ films. Noticeablechanges were observed for TiN, TiO₂, TaN, ZrO₂, and Al₂O₃ from thegraph. With regards to TiO₂, after 1000 etch cycles the thickness of thefilm decreased about 40 nm, consuming the entire layer. After 100 cyclesthe thickness decreased about 20 nm. With regards to TaN, the massdecreased about 22 mg and the sheet resistant increased about 11Ω/□after 1000 cycles. With regards to ZrO₂, the thickness decreased about 5nm after 100 cycles. With regards to Al₂O₃, the thickness decreasedabout 11 nm after 100 cycles.

FIG. 7 is a graph of the weight and sheet resistance changes of TiN andTaN films after varying numbers of ALE cycles with NbF₅ and CCl₄ at areaction temperature of about 450° C. Visual inspection revealedcomplete removal of 20 nm TiN films at the center of the wafer after 400cycles.

FIG. 8 is a graph showing the removed mass (mg) of AlN, TiN, HfO₂, andTaN target films subjected to a variety of thermal atomic layer etchprocesses as described herein and according to some embodiments. Eachtarget film was etched at a variety of reaction, or etching temperaturesfor each process. It was unexpectedly found that an atomic layer etchprocess including NbF₅ as a first reactant and triethylaluminum (TEA) ortrimethylaluminum (TMA) as a second reactant resulted in removed massfrom the TaN and AlN target films.

FIG. 9 is a graph showing the removed mas (mg) of TiN, AlN, AlOx, HfOx,TaN, SiN, and thermal oxide target films subjected to a variety ofthermal atomic layer etch processes as described herein and according tosome embodiments. Each target film was etched at a variety of etchingtemperatures for each process. It was unexpectedly found that ALEprocesses including NbF₅ and TEA as first and second reactants, ALEprocesses using TEA and CCl₄ as first and second reactants, and ALEprocesses using NbF₅, TEA, and CCl₄ as reactants resulted in removedmass from the target films.

It will be appreciated by those skilled in the art that variousmodifications and changes can be made without departing from the scopeof the invention. Similar other modifications and changes are intendedto fall within the scope of the invention, as defined by the appendedclaims.

What is claimed is:
 1. A method of etching a film on the surface of asubstrate in a reaction chamber by chemical atomic layer etching, themethod comprising one or more etching cycles, each cycle comprising:exposing the substrate to a first vapor-phase halide reactant comprisinga first halide ligand to form adsorbed species on the substrate surface,wherein the first vapor-phase halide reactant does not comprisehydrogen; and subsequently exposing the substrate to a secondvapor-phase halide reactant comprising a second halide ligand thatconverts the adsorbed species into volatile species such that at leastsome material is removed from the film, wherein the second vapor-phasehalide reactant does not comprise hydrogen; and wherein the substrate isnot contacted with a plasma reactant during the etching cycle.
 2. Themethod of claim 1, wherein the film comprises W, TiN, TiO₂, TaN, SiN,AlO₂, Al₂O₃, ZrO₂, WO₃, SiOCN, SiOC, SiCN, AlN or HfO_(2.)
 3. The methodof claim 1, wherein the first vapor-phase halide reactant comprise ametal halide.
 4. The method of claim 3, wherein the metal halidecomprises a metal selected from Nb, Ta, Mo, Sn, V, Re, Te, W, and group5 and 6 transition metals.
 5. The method of claim 1, wherein the firstvapor-phase halide reactant does not comprise a metal.
 6. The method ofclaim 1, wherein the first vapor-phase halide reactant comprises anorganic halide compound.
 7. The method of claim 1, wherein the firstvapor-phase halide reactant comprises an alkyl halide, an acyl halide, asulfonyl halide, a sulfenyl halide, a selenyl halide, or a boron halidecomprising an organic ligand.
 8. The method of claim 1, wherein thefirst vapor-phase halide reactant comprises fluorosulfonic acid,trifluoromethanesulfonic acid, trifluoromethyltrifluoromethanesulfonate, sulfur tetrafluoride sulfur chloridepentafluoride or sulfur hexafluoride, or 1-chloro2-(pentafluorosulfuranyloxy)ethane.
 9. The method of claim 1, whereinthe first vapor-phase halide reactant comprises chlorosulfonylisocyanate or N,N-dimethylsulfamoyl chloride.
 10. The method of claim 1,wherein the first vapor-phase halide reactant comprises boron, hydrogen,and a halide.
 11. The method of claim 1, wherein the first vapor-phasehalide reactant comprises phosphorus, oxygen, and a halide.
 12. Themethod of claim 1, wherein the first vapor-phase halide reactantcomprises antimony and a halide.
 13. The method of claim 1, wherein thefirst vapor-phase halide reactant comprises one or more —CF₃ groups. 14.The method of claim 1, further comprising repeating the etching cycletwo or more times sequentially.
 15. The method of claim 1, wherein thefirst and second halide ligands are Cl.
 16. The method of claim 1,wherein the second vapor-phase halide reactant does not comprise metal.17. The method of claim 1, wherein the second vapor-phase halidereactant is a carbon based halide.
 18. The method of claim 17, whereinthe second vapor phase halide reactant comprises CCl₄ or CBr_(4.) 19.The method of claim 1, wherein the temperature of the substrate duringthe etching cycle is 300° C. to 500° C.
 20. A method of etching a filmon the surface of a substrate in a reaction chamber by chemical atomiclayer etching, the method comprising one or more etching cycles, eachcycle comprising: exposing the substrate to a first vapor-phase reactantsuch that the first vapor-phase reactant reacts with a molecule on thesubstrate surface to form reactant species on the substrate surface; andsubsequently exposing the substrate to a second vapor-phase reactantsuch that the reactant species are converted into volatile reactionproducts and a portion of the film is removed from the substratesurface, wherein the substrate is not contacted with a plasma reactantduring the etching cycle, wherein the first vapor-phase reactantcomprises CSe_(2.)
 21. A method of etching a film on the surface of asubstrate in a reaction chamber by chemical atomic layer etching, themethod comprising one or more etching cycles, each cycle comprising:exposing the substrate to a first vapor-phase reactant such that thefirst vapor-phase reactant reacts with a molecule on the substratesurface to form reactant species on the substrate surface; andsubsequently exposing the substrate to a second vapor-phase reactantsuch that the reactant species are converted into volatile reactionproducts and a portion of the film is removed from the substratesurface, wherein the substrate is not contacted with a plasma reactantduring the etching cycle, wherein the first vapor-phase reactantcomprises compounds with S═R═S structure in which R can be carbon or anyhydrocarbon, such as C2-C8.
 22. The method of claim 21, wherein thefirst vapor-phase reactant comprises CS_(2.)
 23. A method of etching afilm on the surface of a substrate in a reaction chamber by chemicalatomic layer etching, the method comprising one or more etching cycles,each cycle comprising: exposing the substrate to a first vapor-phasereactant such that the first vapor-phase reactant reacts with a moleculeon the substrate surface to form reactant species on the substratesurface; and subsequently exposing the substrate to a second vapor-phasereactant such that the reactant species are converted into volatilereaction products and a portion of the film is removed from thesubstrate surface, wherein the substrate is not contacted with a plasmareactant during the etching cycle, wherein the second vapor-phasereactant comprises triethylaluminum (TEA) or trimethylaluminum (TMA).24. A method of etching a film on a substrate in a reaction chambercomprising two or more etching cycles, each cycle comprising: exposingthe substrate to a first vapor-phase halide reactant that does notcomprise hydrogen; and subsequently exposing the substrate to a second,different vapor-phase halide reactant that does not comprise hydrogen;and exposing the substrate to a third vapor-phase reactant that isdifferent from the first and second vapor-phase reactants, wherein thesubstrate is not contacted with a plasma reactant during the etchingcycle.
 25. The method of claim 24, wherein the additional vapor phasereactant comprises one or more ofSO₃, H₂S, NH₃, H2O, HCOOH, H2O2, andhydrazine.
 26. A method for etching a thin film on a substrate surfacecomprising: exposing the substrate surface to a first vapor-phase halidereactant comprising a first halide ligand to form first reactant specieson the substrate surface, wherein the first vapor-phase halide reactantdoes not comprise hydrogen; and subsequently exposing the substrate to asecond vapor-phase halide reactant comprising a second halide ligandsuch that the second vapor-phase halide reactant converts the firstreactant species to vapor phase reaction products, wherein the secondvapor-phase halide reactant does not comprise hydrogen, and, wherein theformation of the first reactant species or the conversion of the secondvapor-phase halide reactant to vapor phase reaction products are notself-limiting.
 27. The method of claim 26, wherein the substrate is notcontacted with a plasma reactant during the etching cycle.
 28. Themethod of claim 26, wherein the formation of the first reactant speciesand the conversion of the second vapor-phase halide reactant to vaporphase reaction products are not self-limiting.